The detection of electromagnetic and nuclear radiation has extensive commercial applications. A variety of detectors including photomultipliers, thermopiles, scintillation devices and solid state detectors are currently used. For example, the thermopile type of detector has a very broad band response since it is based upon thermal conversion of energy absorbed. Unfortunately, this type of detector generally has a slow response time and cannot reasonably be manufactured as two-dimensional array detectors. Solid state detectors for the infrared region are based on semiconductor effects. This generally requires the device to be kept at a cryogenic temperature to reduce thermal activation.
A technique that can detect infrared radiation without requiring temperature control, and that has broadband sensitivity and can be made into two dimensional arrays, would have immediate relevance in a variety of industries, such as: aerospace, military and civilian surveillance, industrial monitoring, night vision systems, and collision avoidance systems.
Similar advantages can be stated for nuclear radiation detectors using micromechanical sensors. Uncooled, integrating detectors having single or arrayed detector elements that respond to absorbed nuclear radiation would have immediate applications in health physics monitoring, mixed waste radiation, environmental monitoring and field screening.
Recently there has been a growth of interest in micromechanical sensors. Micromechanical sensors can consist of any of a class of suspended mass devices, such as microcantilever beams supported at one or multiple points, or suspended about their perimeter. For example, microcantilevers coated with metal on one side undergo bending due to differential thermal expansion of the coating metal and the coated cantilever (the "bimetallic effect"). Bending due to the bimetallic effect has been used for calorimetric detection of chemical reactions with picoJoule (pJ) sensitivity.
U.S. Pat. No. 5,445,008 to Wachter et al. describes microbar sensors which employ microcantilevers oscillated by a piezoelectric transducer. A coating on the beam selectively adsorbs a target chemical, and accumulation of the chemical is manifest in a change of resonant frequency of the beam. This patent is incorporated herein by reference.
U.S. Pat. No. 5,144,833 to Amer et al. describes an atomic force microscope that employs micromachined cantilevers. As a tip mounted on the cantilever moves over a surface, interatomic forces between the tip and the surface induce displacement of the tip.
U.S. Pat. No. 5,245,863 to Kajimura et al. describes another atomic force microscope in which a cantilever is fixed to a piezoelectric element. A semiconductor laser constitutes a Fabry-Perot resonator between a mirror and a reflection cleavage plane. The resonator output varies in accordance with displacement of the cantilever.
U.S. Pat. No. 5,347,226 to Bachmann describes an array spreading resistance probe which uses a microcantilever. A probe tip is formed in openings in the distal end of the cantilever. The probe tips are used to obtain impurity profiles of semiconductors.
U.S. Pat. No. 5,345,816 to Clabes et al. describes an integrated tip strain sensor for use in an atomic force microscope. The tip is formed by electron beam deposition.
The references noted above do not provide methods or devices for measuring atomic or electromagnetic radiations.